A typical modular conveyor belt suitable for being driven by a sprocket built according to this invention is disclosed in U.S. Pat. No. 3,870,141 issued to J. M. Lapeyre on Mar. 11, 1975. According to this patent, substantially identical modules formed by injection molding are pivotally connected to one another to form a conveyor belt or a desired length. Each module includes a plurality of elongated elements, and each elongated element has a first pivot end and a second pivot end. The plurality of elongated elements are joined together such that the apertures defined in each of the first and second pluralities of pivot ends lie along a first and second pivot axis respectively which are parallel one to the other. The link ends of one module are intermeshed and pivotally connected by means of a pivot rod to the link ends of another module until an entire belt having the desired length is formed. Injection molded plastic belts built according to the teachings of this patent have been well received by industry and have many uses.
U.S. Pat. No. 4,051,949 issued Oct. 4, 1977 also to Lapeyre, describes another modular plastic conveyor belt which solved the problem of removing small and/or unstable articles from a conveyor belt without tipping over. The belt provides for a multiplicity of channels formed in the modules which receive the "teeth" of a comb. The belt disclosed in U.S. Pat. No. 4,171,045 also issued to Lapeyre, is similar to that of U.S. Pat. Nos. 3,870,141 and 4,051,949 discussed above, except that selected ones of the vanes include a plurality of "dogs" which extend above the normal portion of the conveying surface to contact and push articles on the conveying surface along such that the belt will not slip underneath.
In a similar manner, U.S. Pat. No. 4,213,527 issued June 22, 1980 to J. M. Lapeyre, et al, further discloses a module for forming a link conveyor belt which has ridges or flight members extending transverse to the direction of travel for preventing the conveyor belt from slipping under articles riding on the conveyor belt surface. Similarly U.S. Pat. No. 4,170,281 issued on Oct. 19, 1979 and U.S. Pat. No. 4,080,842 issued on Mar. 22, 1978, both to Lapeyre, also show conveying belts having members extending transverse to the conveying surface for moving articles on the conveying surface along the belt such that the belt cannot slip underneath the article.
Other modular link conveyor belt patent applications or patents by J. M. Lapeyre and owned by the same assignee as the present invention which are suitable for being driven by the sprocket of this invention, include U.S. Pat. No. 4,832,187 entitled "Modular Center Drive Conveyor Belt" filed Aug. 19, 1980.
Other types of modular plastic conveyor belts produced and manufactured by other than the assignee of this invention include the following:
The "All-in-One".RTM. conveyor belt manufactured by the KVP Company in Sacramento, Calif. and illustrated in FIG. 4 of U.S. Pat. No. 4,742,907 issued May 10, 1988 to Karl V. Palmaer, is a modular plastic belt driven at a central transverse connecting member which can be brick-layed, and therefore can be provided in different widths.
A plastic modular belt sold by the Cambridge Wire Cloth company of Cambridge, Md. under the name of Cam-Clean.RTM. and substantially described in U.S. Pat. No. 4,557,374 issued on Dec. 10, 1985 to Robert H. Bode is driven in the center area of a module by a sprocket tooth received by a recess in the module defined by a pair of transverse connecting members.
Finally, the Rexnord Corp. of Milwaukee, Wis. has recently introduced a group of plastic conveyor belts designated as the "5900" series which uses individual and separate snap-in plugs to retain "headless" pivot rods in position.
Thus, a review of the conveyor belt prior art patents and commercial belts as well as pending applications of the assignee of the present invention reveals that to date there has not been an easy, simple and inexpensive technique for providing a sprocket having a drive surface with increased contact area particularly suitable for high abrasive applications. More particularly, none of the prior art conveying belts or systems teach the fabrication of such sprockets by stacking and aligning similar lamina. Therefore, it is an object of this invention to provide conveyor belt sprockets suitable for use with all types of conveyor belts including modular plastic conveyor belts which have increased drive surface areas and which are easily and inexpensively manufactured.